/**
 * Copyright (C) 2003-2008 eXo Platform SAS.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation; either version 3
 * of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see<http://www.gnu.org/licenses/>.
 */

package org.etk.core.rest.impl.provider;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

import javax.activation.DataSource;
import javax.activation.FileDataSource;
import javax.mail.util.ByteArrayDataSource;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.ext.Provider;

import org.etk.core.rest.RequestHandler;
import org.etk.core.rest.impl.ApplicationContext;
import org.etk.core.rest.impl.ApplicationContextImpl;
import org.etk.core.rest.provider.EntityProvider;


@Provider
public class DataSourceEntityProvider implements EntityProvider<DataSource> {

  /**
   * {@inheritDoc}
   */
  public boolean isReadable(Class<?> type,
                            Type genericType,
                            Annotation[] annotations,
                            MediaType mediaType) {
    return type == DataSource.class;
  }

  /**
   * {@inheritDoc}
   */
  public DataSource readFrom(Class<DataSource> type,
                             Type genericType,
                             Annotation[] annotations,
                             MediaType mediaType,
                             MultivaluedMap<String, String> httpHeaders,
                             InputStream entityStream) throws IOException {
    String m = mediaType != null ? mediaType.toString() : null;

    return createDataSource(entityStream, m);
  }

  /**
   * {@inheritDoc}
   */
  public long getSize(DataSource t,
                      Class<?> type,
                      Type genericType,
                      Annotation[] annotations,
                      MediaType mediaType) {
    return -1;
  }

  /**
   * {@inheritDoc}
   */
  public boolean isWriteable(Class<?> type,
                             Type genericType,
                             Annotation[] annotations,
                             MediaType mediaType) {
    return DataSource.class.isAssignableFrom(type);
  }

  /**
   * {@inheritDoc}
   */
  public void writeTo(DataSource t,
                      Class<?> type,
                      Type genericType,
                      Annotation[] annotations,
                      MediaType mediaType,
                      MultivaluedMap<String, Object> httpHeaders,
                      OutputStream entityStream) throws IOException {
    InputStream in = t.getInputStream();
    try {
      IOHelper.write(in, entityStream);
    } finally {
      in.close();
    }

  }

  /**
   * Create DataSource instance dependent entity size. If entity has size less
   * then <tt>MAX_BUFFER_SIZE</tt> then {@link ByteArrayDataSource} will be
   * created otherwise {@link MimeFileDataSource} will be created.
   * 
   * @param entityStream the {@link InputStream} of the HTTP entity
   * @param mimeType media type of data, HTTP header 'Content-type'
   * @return See {@link DataSource}
   * @throws IOException if any i/o errors occurs
   */
  private static DataSource createDataSource(InputStream entityStream, String mimeType) throws IOException {

    boolean overflow = false;
    byte[] buffer = new byte[8192];

    ApplicationContext context = ApplicationContextImpl.getCurrent();
    int bufferSize = (Integer) context.getAttributes().get(RequestHandler.WS_RS_BUFFER_SIZE);
    ByteArrayOutputStream bout = new ByteArrayOutputStream(bufferSize);

    int bytes = -1;
    while ((bytes = entityStream.read(buffer)) != -1) {
      bout.write(buffer, 0, bytes);
      if (bout.size() > bufferSize) {
        overflow = true;
        break;
      }
    }

    if (!overflow)
      // small data , use bytes
      return new ByteArrayDataSource(bout.toByteArray(), mimeType);

    // large data, use file
    final File file = File.createTempFile("datasource", "tmp");
    OutputStream fout = new FileOutputStream(file);

    // copy data from byte array in file
    bout.writeTo(fout);

    while ((bytes = entityStream.read(buffer)) != -1)
      fout.write(buffer, 0, bytes);

    fout.close();

    return new MimeFileDataSource(file, mimeType);

  }

  /**
   * FileDataSource with preset media type.
   */
  static class MimeFileDataSource extends FileDataSource {

    /**
     * Media type of the data.
     */
    private final String mimeType;

    /**
     * @param file file
     * @param mimeType media type
     */
    public MimeFileDataSource(File file, String mimeType) {
      super(file);
      this.mimeType = mimeType;
    }

    /**
     * Try remove file when object destroyed. {@inheritDoc}
     */
    @Override
    protected void finalize() throws Throwable {
      super.finalize();
      File file = getFile();
      if (file.exists())
        file.delete();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getContentType() {
      return mimeType;
    }

  }

}